linux-kernel - Re: [PATCH 1/3] iio: buffer: remove usage of list iterator variable for list_for_each_entry_continue

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Date:   Sat, 2 Apr 2022 16:37:23 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Jakob Koschel <jakobkoschel@...il.com>,
        Lars-Peter Clausen <lars@...afoo.de>
Cc:     Dan Carpenter <dan.carpenter@...cle.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        Mike Rapoport <rppt@...nel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>
Subject: Re: [PATCH 1/3] iio: buffer: remove usage of list iterator variable
 for list_for_each_entry_continue_reverse()

On Fri,  1 Apr 2022 01:06:30 +0200
Jakob Koschel <jakobkoschel@...il.com> wrote:

> In preparation to limit the scope of the list iterator variable to the
> list traversal loop, use a dedicated pointer to iterate through the
> list [1].
> 
> Since that variable should not be used past the loop iteration, a
> separate variable is used to 'remember the current location within the
> loop'.
> 
> To either continue iterating from that position or start a new
> iteration (if the previous iteration was complete) list_prepare_entry()
> is used.
> 
> Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
> Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>

Hi Jakob,

Series applied to the togreg branch of iio.git and pushed out as testing to let
0-day take a poke at it. Note I'll be rebasing that branch on rc1 once available
before pushing it out for linux-next to pick up.

Note I'm happy to add additional tags if anyone else takes a look at it.

Thanks

Jonathan

> ---
>  drivers/iio/industrialio-buffer.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/industrialio-buffer.c b/drivers/iio/industrialio-buffer.c
> index 208b5193c621..151a77c2affd 100644
> --- a/drivers/iio/industrialio-buffer.c
> +++ b/drivers/iio/industrialio-buffer.c
> @@ -1059,7 +1059,7 @@ static int iio_enable_buffers(struct iio_dev *indio_dev,
>  	struct iio_device_config *config)
>  {
>  	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
> -	struct iio_buffer *buffer;
> +	struct iio_buffer *buffer, *tmp = NULL;
>  	int ret;
> 
>  	indio_dev->active_scan_mask = config->scan_mask;
> @@ -1097,8 +1097,10 @@ static int iio_enable_buffers(struct iio_dev *indio_dev,
> 
>  	list_for_each_entry(buffer, &iio_dev_opaque->buffer_list, buffer_list) {
>  		ret = iio_buffer_enable(buffer, indio_dev);
> -		if (ret)
> +		if (ret) {
> +			tmp = buffer;
>  			goto err_disable_buffers;
> +		}
>  	}
> 
>  	if (indio_dev->currentmode == INDIO_BUFFER_TRIGGERED) {
> @@ -1125,6 +1127,7 @@ static int iio_enable_buffers(struct iio_dev *indio_dev,
>  					     indio_dev->pollfunc);
>  	}
>  err_disable_buffers:
> +	buffer = list_prepare_entry(tmp, &iio_dev_opaque->buffer_list, buffer_list);
>  	list_for_each_entry_continue_reverse(buffer, &iio_dev_opaque->buffer_list,
>  					     buffer_list)
>  		iio_buffer_disable(buffer, indio_dev);
> 
> base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275
> --
> 2.25.1
>